Semiconductor devices for use in networks or digital household electric appliances are desired to be further sophisticated, multifunctional, and low in power consumption. Accordingly, the trend toward micro-patterning for circuits has been developed, with which a pattern collapse of the circuits has been becoming controversial. In semiconductor device fabrication, cleaning steps for the purpose of removing particles and metallic impurities are frequently employed, which results in a 30-40% occupation of the whole of a semiconductor fabrication process by the cleaning step. If the aspect ratio of the pattern is increased with the trend toward micro-patterning of the semiconductor devices, the pattern is to cause its collapse when a gas-liquid interface passes therethrough after cleaning or rinsing at the time of drying the wafer. This phenomenon is pattern collapse.
In Patent Publication 1, there is disclosed a technique of changing a cleaning liquid from water to 2-propanol before a gas-liquid interface passes through a pattern, as a method for suppressing pattern collapse. However, it is said that there are some limitations, for example, an adaptable aspect ratio of pattern is not higher than 5.
Additionally, in Patent Publication 2, there is disclosed a technique directed toward a resist pattern, as a method for suppressing pattern collapse. This is a method of decreasing a capillary force as much as possible thereby suppressing pattern collapse.
However, the technique disclosed as above is directed toward the resist pattern and is for reforming a resist itself. Moreover, a treatment agent can finally be removed together with the resist, so that it is not necessary to estimate a process of removing it after drying; therefore, this technique cannot be applied to the object of the present invention.
Furthermore, Patent Publication 3 discloses a cleaning process for preventing pattern collapse, in which surface-reforming by oxidation or the like is conducted on a wafer surface provided to have an uneven pattern by a film containing silicon, and a water-repellent protective film is formed on the surface by using a water-soluble surfactant or a silane coupling agent to reduce the capillary force.
Additionally, in Patent Publications 4 and 5, there is disclosed a technique of preventing pattern collapse by performing a hydrophobicity-providing treatment with use of a treatment liquid containing a silylation agent (represented by N,N-dimethylaminotrimethylsilane) and a solvent.